(Isthmohyla rivularis)
Males grow to 34 mm (1.3 in) and females to 37 mm (1.5 in) in snout–vent length.The snout is moderately short and acutely rounded.The tympanum is barely discernible.The fingers have large discs and are up to one-third webbed.The toes have discs that are slightly smaller than those on the fingers and are two-thirds webbed.The dorsal color varies from grey to light brown.Most specimens have a thin,dark line running through the eye.Other dark markings are variably present.The flanks are usually yellowish,but may in some individuals appear greenish or bluish.The iris is bronze and has black reticulations